Hydrogen dispensing system and method thereof

ABSTRACT

The invention provides a hydrogen dispensing system comprising: a feed vessel for storing liquid hydrogen having an inlet and an outlet; a flash drum having an inlet and an outlet; a dispenser for dispensing gaseous hydrogen at a pressure of greater than 300 bar, having an inlet and an outlet wherein the feed vessel outlet is in fluid communication with the flash drum inlet, the flash drum outlet is in fluid communication with the dispenser inlet and there is no compression apparatus between the feed vessel outlet and the dispenser outlet. The invention also provides a method of providing gaseous hydrogen to a vehicle.

This is a continuation application from U.S. patent application Ser. No.12/840,159, filed Jul. 20, 2010 which claims the benefit of U.S.Provisional Application No. 61/227,453 filed Jul. 22, 2009.

FIELD

This invention relates to a system for dispensing hydrogen and a methodthereof.

BACKGROUND

In recent years, there has been a great deal of interest in thedevelopment of alternative energy sources, or energy carriers, such ashydrogen. Automobiles and other vehicles that use hydrogen as a fuelsource have been developed, but methods for refueling these vehiclesthat can compete with gasoline fueling stations on scale or cost havenot yet been developed. Gasoline fueling stations are very simple andtypically only consist of tanks for storing the gasoline and one or morepumps. The options that have been developed for hydrogen fueling to dateare expensive, too large and require excessive maintenance.

One option that has been developed provides for storage of gaseoushydrogen at the fueling station and one or more large compressors thatare used to raise the pressure of the hydrogen to the pressure requiredfor fueling, typically from 300 to 700 bar.

This option has a large footprint due to the size and design of thecompressor system as well as high energy usage.

Another option that has been developed provides for storage of liquidhydrogen at the fueling station. The liquid hydrogen is pumped by acryopump to a higher pressure and then it is evaporated to gaseoushydrogen that is used for fueling. Both of these options and the othersknown to those of ordinary skill in the art require mechanicalcompression or pumping to raise the pressure of the hydrogen for use infueling vehicles.

To provide a suitable hydrogen dispensing system, the system must bemuch simpler, cheaper and require less space. In addition, themaintenance requirements and energy use must be reduced to make hydrogenfueling stations a viable alternative to gasoline stations.

SUMMARY

The invention provides a hydrogen dispensing system comprising: a feedvessel for storing liquid hydrogen at a temperature of less than 30 Khaving an inlet and an outlet; a flash drum having an inlet and anoutlet; a dispenser for dispensing gaseous hydrogen at a pressure ofgreater than 300 bar, having an inlet and an outlet wherein the feedvessel outlet is in fluid communication with the flash drum inlet, theflash drum outlet is in fluid communication with the dispenser inlet andthere is no compression apparatus between the feed vessel outlet and thedispenser outlet.

The invention also provides a method of providing gaseous hydrogen to avehicle comprising: storing a liquid hydrogen source in a feed vessel ata temperature of less than 30 K; passing a portion of the liquidhydrogen in the feed vessel to a flash drum; providing sufficient heatto the flash drum to convert the liquid hydrogen to gaseous hydrogen;passing the gaseous hydrogen to a dispenser; passing gaseous hydrogenfrom the dispenser to the vehicle at a pressure of greater than 300 barwherein no compression apparatus is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an embodiment of a hydrogen dispensing system.

DETAILED DESCRIPTION

The invention described herein provides a hydrogen dispensing systemthat provides high pressure gaseous hydrogen without the use of acompression apparatus. A compression apparatus is herein defined as anymechanical apparatus that has moving parts and is used to raise thepressure of a vapor or a liquid such as compressors and pumps, includingcryopumps.

The liquid hydrogen may be prepared by any method and can be transportedto the station by any method known to one of ordinary skill in the art.

Liquid hydrogen inherently comprises very low amounts of contaminants orimpurities. As a consequence, the produced gaseous hydrogen produced byevaporating the liquid hydrogen is also relatively pure.

One embodiment of the system will be described in relation to FIG. 1.FIG. 1 depicts a hydrogen dispensing system. The system has a feedvessel 100 that is suitable for storing liquid hydrogen. The vessel maybe insulated and/or cooled to maintain a temperature low enough thatliquid hydrogen will remain in its liquid state. In one embodiment, thevessel is designed to withstand high pressures as are seen throughoutthe dispensing system. In another embodiment the vessel is designed tofunction at or near atmospheric pressure.

In another embodiment, feed vessel 100 is located underground. This hasthe advantage of lowering the overall footprint.

In a further embodiment, the feed vessel may be provided in the form ofa transportable vessel, in particular a vessel mounted on a trailer,truck, train or other (self-) propelled vehicle. By omitting the need tofill an immobilized storage vessel at the site, the boil-off lossesgenerated during the transfer to the liquid hydrogen into the storagevessel are omitted. Also the delivery time at the station can besignificantly reduced. The feed vessel has an inlet for filling withliquid hydrogen (not shown) and an outlet that is in fluid communicationwith feed line 106. The feed line is used to pass liquid hydrogen fromthe feed vessel 100 to the flash drum 102. The feed line typically has avalve 112 or other device to control the flow of liquid hydrogen to theflash drum.

The system has one or more flash drums 102 that are suitable for holdingliquid and/or gaseous hydrogen. The flash drum is designed such that thetemperature of its contents is greater than the temperature of the feedvessel. The flash drum will function as a heat exchanger and it may infact be a heat exchanger. The flash drum may be heated to provide theheat sufficient to vaporize the liquid hydrogen. The flash drum may beheated by ambient conditions, alone or in combination with anotherheating source. Ambient conditions are defined herein as the temperatureof the environment surrounding the flash drum.

The flash drum may be located inside or outside, so the ambientconditions could be room temperature or the outdoor temperature at thelocation. Insulation may be used to prevent heat loss or to control therate of heat exchange between the flash drum and its surroundings. Inone embodiment, one or more flash drums are located underground. Againthis has the benefit of lowering the overall footprint. In addition,locating the flash drum underground may improve the heating of the flashdrum, due to the better heat conduction properties of the soil comparedto air.

Since the ambient conditions may not be consistent, due to weather orseasonal changes, and also to accelerate the process if necessary, theflash drum may also be equipped with a heat source that can be used toprovide additional heat as needed. Examples of heaters that would besuitable for this application include electrical heaters, steam heatersand heat exchangers that use a heated stream to exchange heat with theflash drum or the liquid hydrogen in the flash drum. In one embodimentthe flash drum could be force heated by a thermoelectric heater, whereinthe temperature difference between the LH₂ and ambient can be utilizedto provide the electricity for heating. In a most simplistic form thiscould consist of a thermo-electric resistive mat on the outside orinside of the bank vessels.

The flash drum has an inlet that is in fluid communication with feedline 106 and an outlet that is in fluid communication with thedispensing line 108. The dispensing line is used to pass gaseoushydrogen from the flash drum 102 to the dispenser 104.

The system has a dispenser 104 that is suitable for dispensing highpressure gaseous hydrogen or a mixture of gaseous and liquid hydrogen toautomobiles or other vehicles. The dispenser may be of any type that canprovide hydrogen. The dispenser may be connected to a vehicle or to ahydrogen tank, cartridge or other storage vessel that is used to providehydrogen to a vehicle. The dispensing line 108 may have a device tocontrol the flow of gaseous hydrogen to the dispenser. Alternatively,the flow of hydrogen may be controlled by the dispenser itself.

In one embodiment, the system comprises a high-pressure line 110 that isused to provide pressure to the head of the feed vessel 100. Inoperation, this line could be used to provide pressure to help move theliquid hydrogen from the feed vessel 100 to the flash drum 102. Thevalve 114 may be opened to allow the pressure of the flash drum 102 tobe communicated to the feed vessel 100. The valve 114 may be closed andreopened as needed to provide additional pressure to the feed vessel.

The feed vessel 100 may be located higher than the flash drum 102 toallow gravity to assist the flow of liquid hydrogen from the feed vessel100 to the flash drum 102. Alternative methods can employ the use oftransfer pumps or differential pressure between the vessels. One ofordinary skill in the art could employ whatever means necessary toensure that there was sufficient force to move the liquid hydrogen fromthe feed vessel 100 to the flash drum 102.

In another embodiment, a compressor may be used to pressurize the feedvessel. A small compressor may be in fluid communication with the highpressure line 110 such that the pressure of the head of the feed vesselwould be higher than the pressure of the flash drum. This would provideadditional force to move the liquid hydrogen to the flash drum. Thecompressor would not be as large as one that would be needed to compressall of the gaseous hydrogen to a high pressure.

In another embodiment, the feed vessel provides liquid hydrogen to anintermediate and smaller cryogenic system supply vessel(s) designed tohandle full system pressures. The interface between the feed vessel andthe supply vessel would be managed by appropriate piping and controls toensure the feed vessel is not exposed to system pressures. The supplyvessel(s) would then pass hydrogen to the flash drum(s) and managementof system pressures and residual gas from the flash drum(s) would beincorporated.

In one embodiment, intermediate storage is used to store the gaseoushydrogen produced in the flash drum 102 before it is dispensed to avehicle via the dispenser 104. This intermediate storage may compriseany method for storing gaseous hydrogen.

The method of producing high pressure hydrogen is outlined below. Asdescribed above, liquid hydrogen is received into the feed vessel 100.The temperature of this vessel is maintained at a temperature to keepthe hydrogen in liquid form. The temperature may be in a range of from 1K to 30 K, preferably in a range of from 15 K to 25 K. Some portion ofthe liquid hydrogen may evaporate in the feed vessel, but it isdesirable to minimize this evaporation.

The liquid hydrogen is fed via the feed line 106 to the flash drum 102.The valve 112 is opened for this step and then closed when the properamount of liquid hydrogen has been fed to the flash drum.

The temperature of the flash drum is such that at least a portion of theliquid hydrogen vaporizes in this vessel. It is preferred that asubstantial portion of the liquid hydrogen vaporizes in this vessel;preferably at least 50%, more preferably at least 75% and mostpreferably at least 90% of the liquid hydrogen. The flash drum is aclosed vessel with a specified volume. The pressure of the gaseoushydrogen is dependent on the amount of liquid hydrogen fed to the flashdrum.

Sufficient liquid hydrogen is fed to the flash drum such that whenvaporized the gaseous hydrogen will be at a pressure of greater than 300bar, preferably greater than 500 bar and more preferably greater than700 bar. The pressure may be in a range of from 200 bar to 1000 bar,preferably in a range of from 300 bar to 800 bar. Depending on theapplication and the requirements of the vehicle being fueled the systemcan be adjusted to provide gaseous hydrogen at multiple pressures. It isunderstood that the hydrogen produced will be at a pressure sufficientto fuel the vehicles including overcoming pressure drop in the system.

In one embodiment, a cascade of flash drums is provided each flash drumin the cascade set to provide high pressure gaseous hydrogen at aspecific pressure, i.e., at 450 bar for those vehicles that require thehydrogen to be fed at 350 bar and at 700 bar for those vehicles thatrequire the hydrogen to be fed at 700 bar. Alternatively, a continuouslyoperated cascade of flash drums is provided. For example, a first flashdrum is filled with liquid hydrogen and the liquid hydrogen supply ishalted. The flash drum is heated to provide gaseous pressure at a highpressure, e.g. 700 bar. As gaseous hydrogen is removed from the flashdrum the pressure drops to pressures below 700 bar. At this time, asecond flash drum, which is full, takes over the supply of high pressuregaseous hydrogen, in this case 700 bar, while the first flash drum isused to provide medium pressure gaseous hydrogen, e.g. 500 bar. Thisprocess is continued until the first (or second) flash drum cannotprovide gaseous hydrogen at sufficient pressure anymore and the firstflash drum is refilled with liquid hydrogen to provide high pressurehydrogen again or optionally a third flash drum is used to provide highpressure gaseous hydrogen while the second drum is directed at providingmedium pressure gaseous hydrogen and the first flash drum is directed atproviding low pressure, e.g. 350 bar, gaseous hydrogen. This procedureoperated continuously. It will be appreciated that the number orincremental pressure steps is dependent of the dispensing requirementsas is the number of flash drums provided in the cascade.

As the hydrogen dispensing procedure and in addition filling of thevehicle hydrogen tank produces significant amounts of heat, there is aneed to provide the gaseous hydrogen at low temperatures. Typically, thegaseous hydrogen is dispensed a temperatures of in the range of from −40to −20° C. Due to the low temperature of the liquid hydrogen, the systemcan be operated to dispense sufficiently cold gaseous hydrogen, withoutthe need to pre-cool the gaseous hydrogen prior to dispensing.

In one embodiment, the system is operated to be able to dispense highpressure gaseous hydrogen at cryogenic temperatures, i.e.cryo-compressed hydrogen, in particular gaseous hydrogen at a pressureof in the range of from 300 to 500 bar, preferably 350 to 400 bar and atemperature of in the range of from 100 to 200 K. Cryo-compressedhydrogen has a higher density compared due to the low temperatureallowing more hydrogen to be stored on board of a vehicle and allowingfor shorter refueling times.

The gaseous hydrogen may be passed directly to the dispenser or it maybe passed to intermediate storage for the gaseous hydrogen. Theintermediate storage may be designed to store hydrogen at multiplepressures, i.e., at 300, preferably 450, bar for those vehicles thatrequire the hydrogen to be fed at 300, respectively preferably 350, barand at 700, preferably 850, bar for those vehicles that require thehydrogen to be fed at 700 bar. The intermediate storage may becontinuously operated as described herein above for the cascade of flashdrums.

The system may additionally comprise a dispenser for dispensing liquidhydrogen or a mixture of gaseous and liquid hydrogen directly from thefeed vessel. In this way the system could be designed to meet differentrefueling requirements and could for example, refuel vehicles withliquid hydrogen and with gaseous hydrogen at pressures up to 700 bar.

The invention claimed is:
 1. A method of providing gaseous hydrogen to avehicle comprising: a. storing a liquid hydrogen source in a feed vesselat a temperature of less than 30 K; b. passing a portion of the liquidhydrogen in the feed vessel to a first flash drum; c. passing a portionof the liquid hydrogen in the feed vessel to a second flash drum; d.providing sufficient heat to the first flash drum to convert at least aportion of the liquid hydrogen to gaseous hydrogen; e. passing thegaseous hydrogen from the first flash drum to a dispenser; f. when thepressure of the gaseous hydrogen from the first flash drum drops tobelow a first pressure, providing sufficient heat to the second flashdrum filled with liquid hydrogen to convert at least a portion of theliquid hydrogen to gaseous hydrogen to provide gaseous hydrogen at orabove the first pressure; g. passing the gaseous hydrogen from thesecond flash drum to the dispenser; and h. passing the gaseous hydrogenfrom the dispenser to the vehicle at a pressure of greater than 300 barwherein no compression apparatus is used.
 2. A method as claimed inclaim 1 wherein the gaseous hydrogen is passed from the dispenser at apressure of greater than 700 bar.
 3. A method as claimed in claim 1wherein the heat to the first and second flash drums is provided byexposure of the first and second flash drums to ambient temperatures. 4.A method as claimed in claim 1 further comprising passing at least aportion of the gaseous hydrogen to a storage vessel before passing it tothe dispenser.
 5. A method as claimed in claim 1 wherein heat to thefirst and second flash drums is provided by a heat source that providesa greater heat flux than that provided by exposure to ambientconditions.
 6. A method as claimed in claim 1 wherein the heat to thefirst and second flash drums is provided by the flash drums functioningas heat exchangers.
 7. A method as claimed in claim 1 wherein a highpressure line is used to provide pressure to the head of the feed vesselto help move the liquid hydrogen from the feed vessel to the flashdrums.
 8. A method as claimed in claim 1 wherein the feed vessel islocated higher than the flash drums to allow gravity to assist the flowof liquid hydrogen from the feed vessel to the flash drums.
 9. A methodof providing gaseous hydrogen to a vehicle comprising: a. storing aliquid hydrogen source in a feed vessel at a temperature of less than 30K; b. passing a portion of the liquid hydrogen in the feed vessel to afirst flash drum; c. passing a portion of the liquid hydrogen in thefeed vessel to a second flash drum; d. providing sufficient heat to thefirst flash drum to convert at least a portion of the liquid hydrogen togaseous hydrogen; e. passing the gaseous hydrogen from the first flashdrum to a dispenser; f. providing sufficient heat to the second flashdrum filled with liquid hydrogen to convert at least a portion of theliquid hydrogen to gaseous hydrogen; g. passing the gaseous hydrogenfrom the second flash drum to the dispenser; and h. passing the gaseoushydrogen from the dispenser to the vehicle at a pressure of greater than300 bar wherein no compression apparatus is used.
 10. A method asclaimed in claim 9 wherein the gaseous hydrogen is passed from thedispenser at a pressure of greater than 700 bar.
 11. A method as claimedin claim 9 wherein the heat to the first and second flash drums isprovided by exposure of the first and second flash drums to ambienttemperatures.
 12. A method as claimed in claim 9 further comprisingpassing at least a portion of the gaseous hydrogen to a storage vesselbefore passing it to the dispenser.
 13. A method as claimed in claim 9wherein heat to the first and second flash drums is provided by a heatsource that provides a greater heat flux than that provided by exposureto ambient conditions.
 14. A method as claimed in claim 9 wherein theheat to the first and second flash drums is provided by the flash drumsfunctioning as heat exchangers.
 15. A method as claimed in claim 9wherein a high pressure line is used to provide pressure to the head ofthe feed vessel to help move the liquid hydrogen from the feed vessel tothe flash drums.
 16. A method as claimed in claim 9 wherein the feedvessel is located higher than the flash drums to allow gravity to assistthe flow of liquid hydrogen from the feed vessel to the flash drums. 17.A method of providing gaseous hydrogen to a vehicle comprising: storinga liquid hydrogen source in a feed vessel at a temperature of less than30 K, passing a portion of the liquid hydrogen in the feed vessel to afirst flash drum via a feed line connected to the feed vessel and thefirst flash drum; closing a valve coupled to the feed line after thefirst flash drum is filled with an amount of liquid hydrogen;vaporizing, in the first flash drum, at least a portion of the liquidhydrogen to provide gaseous hydrogen at a pressure of greater than 300bar in the first flash drum; passing a portion of the liquid hydrogen inthe feed vessel to a second flash drum; closing a valve coupled to aninlet of the second flash drum after the second flash drum is filledwith an amount of liquid hydrogen; vaporizing, in the second flash drum,at least a portion of the liquid hydrogen to provide gaseous hydrogen ata pressure of greater than 300 bar in the second flash drum; passinggaseous hydrogen in the first flash drum to a dispenser and from thedispenser to a vehicle at a pressure of greater than 300 bar; andpassing gaseous hydrogen in the second flash drum to the vehicle usingthe dispenser when the pressure in the first flash drum is insufficientto provide gaseous hydrogen to the vehicle, wherein there is nocompression apparatus between the feed vessel outlet and the dispenseroutlet.
 18. A method as claimed in claim 17 further comprising passing aportion of the liquid hydrogen in the feed vessel to the first flashdrum when the pressure in the first flash drum is insufficient toprovide gaseous hydrogen to the vehicle.
 19. A method as claimed inclaim 17 wherein the gaseous hydrogen is passed from the dispenser at apressure of greater than 700 bar.